1. Field of the Invention
This invention relates to shuttle mechanisms and is particularly applicable to the lens shuttle mechanism for a microfilm camera.
A requirement in many shuttle mechanisms is to provide accurate linear motion of a shuttle member relative to a base member, and in particular in a microfilm camera it is necessary to provide linear motion of the lens while maintaining sharp focus.
2. Description of the Prior Art
One particular known lens shuttle mechanism is based on the Watt straight line mechanism. The lens is centrally situated on a cross member which is carried by leaf springs or flexures of equal length attached to respective ends of the cross member so that they extend perpendicular to the cross member in opposite directions. The outer ends of the two flexures are molded into the camera body and the desired linear motion of the lens is produced by a connecting rod attached to the cross member and is driven by means of a crank arm fitted to a servo motor. This mechanism suffers from the following disadvantages:
1. The ends of the flexures which are molded into the camera body are, due to their distance apart, affected by any dimensional instability of the camera body. This has to be made extremely rigid, as any movement of the flexures is detrimental to the resolution of the camera.
2. The performance of the mechanism is affected by the tolerances on the camera body.
3. The focal plane requires adjustment using a dial gauge and a surface plate.
4. Any movement of the servo motor due to reactionary forces or vibration results in a positional error.